i think i am on the way solving it :D, i use a game instance where i make a array where i store all spawned cubes (just like Pariah013 said), and on my level bp i use “event end play” and cast to my game instanc, and destroy the cubes 
i just need to figure out how to control what cube still there so it dont try to destroy something that is not there :), well if there are better ways please tell me, maybe i do this way to complicated?